This invention relates to an overcurrent protection apparatus utilizing a microcomputer for providing overcurrent interrupting characteristics having a capability to coordinate with other protection apparatus characteristics concerned with high precision.
In an ordinary overcurrent protection apparatus wherein an abnormal current flowing through a power line is detected for tripping a circuit breaker provided in the power line, it is essential that the overcurrent interrupting characteristics with coordinating capability have a performance which implements a specified coordination curve precisely. Heretofore, various attempts have been made for providing an overcurrent protection apparatus of the aforementioned type with the use of, for instance, an electronic circuit or a magnetically balancing type device. However, most of these apparatus require too many electronic components, or have insufficient capability in keeping the preset interruption characteristics immunized from the influence of ambient variations.